Vertical mixer construction



Oct. 6, 1964 R. M. BROOMALL 3,151,847

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Oct. 6, 1964 R. M. BROOMALL VERTICAL MIXER CONSTRUCTION 8 Sheets-Sheet 5 Filed March 19, 1962 Arroe/veys.

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VERTICAL MIXER CONSTRUCTION Filed March 19, 1962 8 Sheets-Sheet 4 Oct. 6, 1964 R. M. BROOMALL 3,151,847

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Filed March 19, 1962 R. M. BROOMALL VERTICAL MIXER CONSTRUCTION 8 Sheets-Sheet 6 Oct. 6, 1964 R. M. BROOMALL VERTICAL MIXER CONSTRUCTION 8 Sheets-Sheet 7 Filed March 19, 1962 W $552122 wmm fzim AT 702N575.

Oct. 6, 1964 R. M. BROOMALL VERTICAL MIXER CONSTRUCTION Filed March 19, 1962 8 Sheets-Sheet 8 I l I l I I United States Patent 3,151,847 VERTlCAL WEEK CGNSTRUCTTDN Robert M. Broomall, Fort Thomas, Ky, assignor to The 5. E. Day Company, a corporation of Delaware Filed Mar. 19, 1962 Ser. No. 184,629 14- Qlaims. (El. 259-129) The present invention relates to mixers and is particularly directed to a novel vertical mixer in which material is subjected to both a thorough mixing action and a kneading action in which substantial shear forces are imposed upon the material.

There are at the present time in various chemical industries many materials which must be mixed in a very exacting manner under carefully controlled conditions. By Way of example, in the processing of rocket propellant fuels, it is necessary to obtain a complete dispersion of an oxidizer such as ammonium perchlorate ground into small particles in a plastic, resinous or elastomeric fuel material such as polysulfide rubber. At the same time, it is necessary that there be effected a thorough mixing of various catalysts, inhibitors and other minor additives. Finally, it is necessary to obtain a maximum packing or densification of the particulate oxidizer material. The difficulties involved in mixing materials such as a rocket fuel propellant are compounded by the fact that the material must not be contaminated during the mixing as, for example, by contact with any oil from the mixer. Also, it is necessary that the material be mixed under a high vacuum.

The principal object of the present invention is to provide a mixer which is effective to mix chemicals with a mixing action which is substantially more efiicient than that of any mixers available at the present time. Thus, the present mixer not only obtains an optimum mixture of the material but does so in only a fraction of the time previously required. By way of example in one test run, the present mixer was effective to complete a mixing operation in approximately thirty minutes which previously required six hours to perform on a conventional mixer. The effectiveness of the present mixer is due in part to the fact that the mixer combines two distinctly different types of action upon the material being mixed. In the first place, the mixer exerts a mixing action on the material so that the batch is made homogeneous and the various components of the mixture are completely dispersed throughout the entire mix. In the second place, the mixer exerts a kneading or squeezing action on the material so that the material is subjected to relatively high shear forces and any agglomerates are broken up and dispersed.

Another object of the present invention is to provide a mixer in which material can be subjected to a vigorous mixing action under a vacuum without contaminating the processed material with any oil or other lubricant from the mixing machine.

More particularly, the present invention is predicated in part upon the concept of providing a vertical mixer having three depending agitator shafts which carry coopcrating agitator blades of a unique configuration. In the present mixer, the center agitator shaft rotates about a stationary axis and carries an agitator having four spiral arms extending outwardly therefrom. The two other shafts of the mixer move in a planetary movement around the center agitator shaft and at the same time rotate about their own axes. Each of these outer, or planetary shafts, carries an agitator blade having two spiral arms extending outwardly therefrom. The planetary shafts move planet-wise in the reverse direction of rotation as that of the center shaft. In addition, these shafts rotate upon their own axes in the reverse direction to the direction of rotation of the center shaft.

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The center agitator of the present mixer comprises four identical spiral arms extending outwardly from the hub of the agitator at substantially intervals. Each of these arms includes a concave leading surface and a convex trailing surface joined by an outer tip. Each of the outer agitators includes two identical arms spaced apart. Each of these outer arms also includes a concave leading surface and a convex trailing surface which meet at an outer tip. As is explained in detail below, the concave leading face of each of the center arms is configurated so that the cooperating tip of the outer arm sweeps along the concave leading face and is spaced from it only by a small uniform clearance distance, or example, an eighth of an inch. In a similar manner the trailing face of the outer agitator blade is configurated so that the tip of the cooperating center blade sweeps over the trailing surface of the outer blade and clears that blade by a uniform clearance distance again of approximately an eighth of an inch. Additionally, the concave leading surface, the tip edge and the convex trailing surface of each of the arms of the center and outer blades is angulated with respect to the axis of the blades in the nature of a helix. Specifically, the helix angle of each of the blades extends upwardly and forwardly from the bottom of the blade to the top of the blade in the direction of rotation of the blade, the helix angle of the center blade being substantially one-half that of the outer blades. For example, in one preferred mixer the center agitator has a helix angle of 15 while the outer blades have a helix angle of 30.

As the blades rotate, the arms of the outer blades first sweep along the rim of the bowl and force material inwardly toward the center of the bowl. During the inward portion of its movement, the tip of each outer agitator blade in turn passes adjacent to the tip of one of the arms of the center blade. The tip of the arm of the outer blade then passes inwardly and sweeps along the leading surface of the center blade arm. At the same time, the tip of the arm of the center blade sweeps along the trailing surface of the same arm of the outer blade. As the blades interrnesh, the entire leading surface of the center blade arm and the trailing surface of the outer blade arm extend substantially parallel to one another and are spaced only a small distance apart. Since these surfaces of substantial area are moving transverse to one another, a very effective shearing and kneading action is exerted upon the material being processed. At the same time, the helix angle of the blades forces the material downwardly toward the bottom of the container from the top which contributes to the efliciency of the kneading and mixing action.

These and other objects and advantages of the present invention will be more readily apparent from a consideration of the following detailed description of the drawings illustrating one preferred form of the invention.

In the drawings:

FIGURE 1 is a perspective view of a mixer of the present invention showing a mixer bowl in position to be elevated up into the mixing position.

FIGURE 2 is a perspective view of the mixer shown in FIGURE 1 illustrating the mixer bowl in the mixing position.

FTGURE 3 is an elevational view of one set of mixing blades of the present invention.

FIGURE 4 is a diagrammatic top plan view of the mixer blades as the blades approach the position of maximum intermesh.

FIGURE 5 is a diagrammatic top plan view of the mixer blades showing the blades at a slightly later point in the operating cycle.

FIGURE 6 is a top plan schematic view showing the position of the mixer blades at a still later time as the cooperating blades start to separate from one another.

FIGURE 7 is a vertical cross sectional view taken along line 77 of FIGURE 2.

FIGURE 8 is an enlarged cross sectional view of the head of the mixer.

FIGURE 9 is a cross sectional view of the center agitator blade showing the relationship between the configuration of this blade and the locus of movement of the tips of the outer agitator blades relative to the center blade.

FIGURE It: is a cross sectional view of an outer agitator blade showing the relationship of this blade to the locus of movement of tips of the center blade relative to the outer agitator blade.

One preferred form of mixer 16 constructed in accordance with the principles of the present invention is shown in FIGURE 1. As there shown, the mixer comprises a base ll, 21 lower housing section 12 and an upper housing, or head enclosing housing 13. A motor 14 is mounted rearwardly of upper housing 13. Mixer it includes three depending vertical shafts, a center shaft 15 and two outer, or planetary shafts 16 and 17. Each of the shafts l5, l6 and 17 has a mixer blade 18, 2d and 21 respectively secured thereto.

Mixer blade 18, mounted upon center shaft 15, has four spiral arms extending outwardly therefrom, while each of the blades 2% and 21 mounted upon outer shafts 16 and 17 has two spiral arms extending outwardly. Housing 13 encloses a drive mechanism 22 effective to rotate center shaft 15 about a stationary axis. This sme drive mechanism is effective to drive the shafts i6 and 1'7 in a planet-wise movement about the center shaft 15. At the same time each or" the shafts l6 and 17 is rotated about its own axis.

The material being mixed is carried in a bowl 23. In the embodiment shown, bowl 23 is rolled into position beneath the mixing head by means of wheels 24. Once the bowl is positioned beneath the agitator shafts and mixer blades, the bowl is elevated and supported by means of a bowl elevating mechanism indicated general- 1y at 25'. When the bowl is supported in the mixing position, the upper rim 26 of the bowl seats against a lower shoulder 27 formed as part of a shroud assembly 23 mounted within upper housing member 13. Two vacuum lines 39 and 31 communicate with the vacuum shroud assembly so that a vacuum can be drawn both upon the mixing bowl 23 and the head drive 22.

The details of construction of the mixer head and housing are best shown in FIGURES 7 and 8. As is there shown, lower housing 12 comprises a rear panel 32 and side panels 33 joined to upper inwardly extending flanges 34. These flanges 34 in turn abut flanges or shoulders 27 formed as part of shroud assembly 28. The shroud assembly includes upstanding side walls 35 which are joined at their lower end in airtight relationship to flange 27 and at their upper edge to top plate 36. An annular divider plate 37 extends transverse across shroud 28 at a point spaced upwardly from flange 27. As is explained in detail below, this ring functions to prevent the material being mixed from contaminating the lubricating oil by providin a seal between the space below the mixer head, and the mixer head and annular space 38. The transverse ring is preferably made of stainless steel and together with liner members 48 made of stainless steel also functions to keep the material from being contaminated by the shroud wall or head assembly.

The top plate, or platen 36, carries a center post member 41. This center post member depends from the platen and is secured thereto as by means of bolts 42. Center post 41 is a rigid member which has an enlarged vertical bore formed therein for receiving center shaft 15. Center post 41 supports an upper set of bearings 43 and a lower set of bearings 44 for rotatably journalling the center shaft. Center post 41 also includes an annular wall section 49 which supports a main load bearing 45 A for rotatably journalling and supporting head assembly 46. In addition to these elements, center post 41 also carries a stationary sun gear 47. This gear surrounds the center post and is held in place by means of a large retaining ring 48 which is bolted to center post 41 as by means of bolts 50.

Head assembly 45 includes a heavy, cylindrical upstanding side Wall member 51. This member is bolted to a rotatable top plate 52 as by means of bolts 53. Rotatable top plate 52 in turn includes an inner cylindrical flange for engaging main load bearings 45. Top plate 52 is bolted as by means of bolts 54 to a thrust ring 55 which also engages main load bearings 45.

An access door 56 is bolted over an opening formed in cylindrical side wall 51. The lower end of wall 51 supports a main transverse plate 57 of the head assembl the transverse plate being secured to cylindrical wall 51 in any suitable manner, such as by means of bolts 58. Transverse wall 57 has a center opening therein for receiving a bearing 66 which is rotatably journalled upon center agitator shaft 15. Transverse wall 57 also carries bearings 61 and 62 which rotatably journal outer agitator shafts 16 and 17.

Cylindrical enclosures 63, 54 and 65 forming part of the lubrication system are welded or otherwise secured to the undersurface of transverse wall 57 surrounding each of the agitator shafts 15, 16 and 17. Each of these lubrication cylinders houses an upper sealing ring 66 and a lower sealing ring 6'7 spaced from one another. A tube, such as tube 58, shown in FIGURE 8 is interconnected to the annular space between the upper and lower gasket rings of each of the enclosures 63, 64 and 65. Tubes 68 (the tubes joined to enclosures 63 and 65 are not shown) are connected to the outlet port of a gear driven pressure pump. This pump (not shown) is mounted upon the upper surface of the transverse wall 57. The pump includes a gear which meshes with drive gear 7t) which is carried by center agitator shaft 15 and is keyed thereto for rotation with that shaft.

Each of the agitator shafts 15, 16 and 17 is provided with a vertical bore 71 and transverse bores 72 in communication with the annular space in enclosures 63, 64 and 65 respectively. Oil introduced through tubes 68 enters the chambers 63, 64 and 65. and flows from these chambers through transverse bores 72 and vertical bores 71 to lubricate the various bearings and gears of the head drive in a manner explained in detail below.

Head assembly 46 also includes a dry well, or oil trap 73. Well 73 comprises a depending cylindrical skirt member 74 which is welded or otherwise secured to cylindrical wall 51 of the head assembly and extends downwardly beneath transverse wall 57. The upper end of skirt 74 revolves within transverse ring. 37. A seal is effected between skirt 74 and this ring by means of an annular gasket '75 which is clamped in place by a retaining ring 76 bolted to transverse ring 37 as by means of bolts 77.

Well 73 also includes a bottom plate 78, preferably formed of stainless steel. This bottom plate is secured to skirt member '74 in any suitable manner, such as by means of bolts 89. Bottom wall 78 carries three gasket clamping rings 81, 82 and 83 which are bolted or otherwise secured to the bottom wall surrounding agitator shafts 15, in and 17. Suitable gaskets 84, 85 and 86 are held by these rings in sealing engagement with the peripheries of stainless steel sleeves 87, 83 and 99 which are fixed to agitator shafts 15, 16 and 17 respectively.

As is best shown in FIGURE 8, each of the agitator shafts 15, i6 and 17 carries a deflector plate disposed in the space above gaskets 84 and their retaining rings and below cylindrical housings 63, 64 and 65. Each of the deflector rings Wt, 2 and 93 is of a diameter greater than the diameter of gasket retaining rings 81, 82 and 83 and includes a downwardly beveled outer edge 94. Deflector rings 91, 92 and 93 are bolted to a radial mount- U ing flange 95 which is welded or otherwise secured to each of the agitator shafts 15, 16 and 17. As is explained in detail below, the function of the deflector rings is to prevent any oil leaking past seals 66 and 67 from dropping into the space between the agitator shafts and gaskets 84, 85 and 86 and possibly leaking through these gaskets into the interior of the bowl 23 to contaminate the material being processed. Rather, any small amount of oil dropping onto the deflector plates drops directly onto the bottom plate 78 of the well. Since this bottom of the well is a substantial distance below the juncture 96 between the rotating agitator shafts and the retaining rings 81, 82 and 83, a considerable volume of oil must accumulate in the well before there is a possibility that any of the oil can leak past gaskets 86 and into the mixing bowl.

Agitator shafts 15, 16 and 17 are driven from an electrical motor 14 mounted upon a suitable frame structure 97 secured to the mixer housing. The output shaft 93 of motor 14 carries a drive pinion 1% which meshes with a drive chain 1111. This chain in turn meshes with a driven pinion 1-32 mounted upon a sleeve 133 which is keyed to the upper end of agitator shaft 15. Gear 1132 is carried by a radial flange 194- formed upon sleeve 1G3 and is connected in driving relationship with the sleeve by means of a shear pin 105. The upper end of shaft 15 is journalled in a bearing 1-95 carried by a frame member 107. Shaft 15 passes downwardly through an opening provided in a plate 168 bolted over an opening in top platen member 36. Plate 1% carries a sleeve 110 which surrounds agitator shaft 15 and carries a plurality of sealing rings 111. As is shown in FIGURE 7, the upper and lower rings are spaced from one another and are connected to a vacuum line 112.

Shaft 15 is driven in a clockwise direction, as viewed in FIGURES 4, 5 and 6. The center agitator shaft carries a main drive gear 71? which is keyed to the shaft. This gear in turn meshes with driven gears 113 and 114 which are keyed to the outer agitator shafts 16 and 17. Each of the agitator shafts 16 and 17 also has a second set of gear teeth 115 and 116 machined thereon for engagement with stationary sun gear 47.

The upper end of each of the agitator shafts 16 and 17 is rotatably journalled in a thrust bearing 117 supported in a suitable opening formed in rotatable top plate 52 of the head assembly. The bearings are held in place by retaining rings 118 which are bolted to plate member 52. A thrust ring is threaded over the end of each of the agitator shafts 16 and 17 for engagement with bearings 117. As was explained above, each of the agitator shafts is also supported by a bearing 61, 62 carried by main transverse wall 57 of the head assembly. By virtue of the gear drive just explained, agitator shafts 16 and 17 are driven in a planet-wise movement counterclockwise about center agitator shaft 15 as viewed in FIGURE 4. At the sarne time, each of the agitator shafts 16 and 17 is rotated about its own axis in a counterclockwise direction at a rate of rotation twice that of the center agitator shaft. The rate of orbital rotation of the shafts 16 and 17 varies but is such that the top speed of the agitator blades 24) and 21 does not substantially exceed thirty four hundred inches per minute. This value has been empirically determined to be the approximate upper limit of tip speed which gives efiective mixing action.

Center agitator shaft 15 carries agitator blade 18. Blade 18 is mounted upon the lower end of shaft 15 in any suitable manner, for example by press fitting the blade over the end of the shaft and then passing a transverse pin (not shown) through aligned openings in the blade and shaft. Outer agitator shafts 16 and 17 carry blades 29 and 21 which are mounted upon the ends of the respective agitator shafts in the same manner.

Agitator blade 18 includes a hub section 12?? and four outwardly extending spiral arms 121, 122, 125 and 124.

Each of these arms is identical with arm 123 so only that arm will be described in detail. Arm 123 includes a leading edge 125 presenting a generally concave face to the process material as the arm is advanced. The arm includes an outer tip 125 and a convex trailing face 127. The leading surface of arm 123 merges smoothly with the trailing surface of arm 124 to form a continuous surface of generally S-shaped configuration. In a similar manner, the trailing edge of arm 123 merges with the leading edge of arm 122 in a surface of generally S shape. As is shown in FIGURE 4, the four arms 121, 122, 123 and 124 are equispaced from one another so that the arms are approximately apart. It is to be understood that the semi-diagrammatic view of FIGURE 4 shows the shape of the blade 18 as it would appear in a transverse cross section. In fact, each of the arms 121, 122, 123 and 12-: is helical in cordiguration, the helix advancing from the top to the bottom of the agitator blade in the direction of the blade rotation. A preferred helix angle is approximately 15 As is shown in FIGURE 3, the tip portion 126a at the top of blade 122 is approximately 15 ahead of the tip portion 1215b at the bottom of the blade. Each of the arms 121, 122, 123 and 12 iembodies this same 15 helix angle.

Center agitator blade 18 cooperates with two planetary blades 2% and 21. The blades 21 and 21 include hub sections 128429 which are mounted upon the ends of shafts 16 and 17 in the same manner that agitator 13 is mounted on the lower end of shaft 15. Each of the agitator blades 21 and 21 comprises two arms 13% 131, 132 and 133. Blades 21 and 21 rotate in a counterclockwise direction as is shown in FIGURE 4 at a rate twice the rate of rotation of blade 18. At the same time, the shafts 16 and 17, which carry blades 26; and 21, move counterclockwise in a planetary movement around center shaft 15.

Each of the blades 21; and 21 is identical so that only blade 21? will be described in detail. The urns 131? and 131 of blade 2% are disposed along a substantially diametral line. Each of these arms comprises a leading surface 134 which presents a generally concave face to the material as the blade advances. Each arm also encloses a tip 135 at the outer edge of the leading surface and a convex trailing surface 156. As shown in FIG- URE 4, there is a slight undercut portion 137 at the juncture of the trailing edge 136 and hub section 1215.

Again, the configuration of agitator blades 2% and 21 in FIGURE 4 represents a transverse sectional view through the blades. In fact, as is shown, in FIGURE 3, each of the agiator blades is helical in shape. he helix angle of these blades again extends from the bottom to the top in the direction of advancement of the blades. This helix angle is substantially twice the helix angle of the center blade 1%. Thus, as is shown in FIGURE 3, the top point 135a of tip 135 is approximately 30 ahead of the lower edge of the tip 135i). It is to be understood that each of the arms 136, 131, 132 and 133 has the same helix axis.

During operation of the mixer, each of the tips 135 of arm 131 and 132 is brought into proximity with tip 126 of center agitator arms 123 and 121 respectively. Due to the fact that the agitators 2t and 21 are rotating at twice the speed of center agitator 13 and at the same time are moving in a planet-wise movement about the center agitator, tips 135 sweep the leading surfaces of arms 123 and 121. They also sweep a portion of the trailing surfaces of arms 124 and 122 as is indicated in FTGURE 5. At the same time, tips 1'26 of arms 123 and 121 of the center agitator sweep along the trailing surfaces 136 of arms 131 and 132. During this movement, the trailing surface 136 and the leading surface 125 of the outer arms and center agitator arm respectively extend generally parallel to one another and are moving transverse to one another at a distance of approximately one-eighth of an inch so that a very effective kneading action in which the material is subjected to substantial shear forces is achieved. When the adjacent blade surfaces separate as is shown in EZGURE 6, tip 135 of the blade 131 starts to move outwardly toward the liner of bowl 23. As it moves outwardly it passes within an eighth of an inch or so of the bowl and then starts to move inwardly again. Simultaneously, the tip of arm 13% sweeps the leading surface of arm 122 and the tip of arm 133 sweeps the leading face of arm 124. Subsequently, the tip of arm 131 sweeps the leading face of arm 121 while the tip of arm 132 sweeps the leading face of arm 123.

The manner in which the exact configuration of the arms of center agitator 18 is obtained can best be seen in FIGURE 9. FIGURE 9 shows a sectional view through the agitator blade together with two lines 138 and 139. Line 138 represents the locus of movement of tip 135 of arm 131 relative to the center agitator 13. The line 139 represents the locus of the tip of arm 13% relative tocenter agitator 18. As can be clearly seen in FIGURE 9, the locus of tip 135 of arm 131 is such that it moves inwardly along the leading surface of arm 123 and a portion of the trailing surface of arm 124 and then moves outwardly toward the wall of the bowl. Subsequently, the tip moves inwardly along the leading surface of arm 121 and a portion of the trailing surface of arm 122. Thereafter, the tip again moves outwardly toward the surface of the bowl before it starts to move inwardly to again sweep the surface of arm 123.

The configuration of center agitator 18 is determined by plotting this locus and then conforming the surface of the agitator arms to the locus (allowing only for a predetermined clearance, for example one-eighth of an inch) from the time that the locus of the tip 135 moves within the radius of the arms 123 etc. of center agitator 18 as at point 149 until the tip 135 has advanced through its point of deepest penetration as at point 141 and has returned a substantial distance out toward the radius of arm 123 as indicated at point 142. While the exact shape of the convex bulge 1 13 in trailing edges 127 is not critical, I have empirically determined that by providing an exaggerated bulge at this point a slightly improved mixing action is achieved.

The design of the planetary blades 20 and 21 is best shown in FIGURE 10. This figure shows a planetary blade 29 and two lines 144 and 145 which represent the locus of movement of tips 126 of center agitator arms 121, 122, 123 and 124 relative to the agitator blade 20. Specifically, line 144- represents the locus of tips 126 of arms 123 and 121, while line 145 represents the locus of tips 126 of arms 122 and 124.

As is shown in FIGURE 10, the critical surface on the outer agitator blades is the trailing surface 136 on each of the arms. The contour of this surface is determined by the locus of tip 126 from the time that it reaches the maximum radius of arm 131 as at point 146 until the locus of point 126 passes inwardly to its point of deepest penetration adjacent to hub 128 as at point 147, makes a loop indicated at 148 and again crosses the locus line and continues to move outwardly. Again, of course, the desired clearance distance is left, in this case an eighth of an inch, between the locus of tip 126 and the trailing surface 136 of the agitator arm. It should be noted that the loop 14% in the locus of point 126 gives rise to the necessity of undercut portion 137 at the juncture of the trailing surface 136 and hub portion 128.

FIGURE 7 shows the cooperative relationship of blades 18, 2t) and 21 within bowl 23. It is to be understood that the bowl is held in position in any suitable manner. For example, the outer rim of the bowl may be provided with downwardly opening recesses for receiving transverse pins carried by the piston rods of hydraulic pistons (not shown) effective to lift the bowl and hold it in airtight engagement with flange 27. With the bowl in this position, a vacuum is drawnon the bowl through tube 31. In a similar manner a vacuum is drawn on the upper head through line 311, these lines being connected to any suitable vacuum pump.

In operation, a bowl filled with material to be mixed is raised into position as shown in FIGURE 2. Thereafter, a vacuum is drawn on lines 311 and 31 and on tube 112. If necessary or desirable, a liquid may be circulated through a cooling jacket 15% fitted around bowl 23 so that the process material can be kept not only under the desired pressure but also at a desired temperature. When motor 14 is energized, it is effective to rotate center shaft 15 through drive chain 101. As the center shaft 15 rotates, it carries center agitator 18 with it, rotating that agitator in a clockwise direction.

At the same time, agitator shafts 16 and 17 are driven from main gear 70. These shafts thus rotate about their own axes. However, the engagement of gears and 116 carried by these shafts with stationary sun gear 47 also causes the head assembly 46 and agitator shafts 16 and 17 to be moved in a counterclockwise direction at a rate of sli htly in excess of one-half times the rate of rotation of the center agitator. As was explained previously, the planetary agitators 2t) and 21 rotate in a counterclockwise direction at a rate of speed twice that of the center agitator 18. These outer agitators are effective to scrape the outer surface of the bowl and to force material inwardly. The material adjacent the center of l-l bowl is subjected to a very high shearing and kneading force as the leading surface of the center agitator arms pass parallel and closely adjacent to the trailing surfaces of the outer agitator arms. At the same time, the helix angles of the agitators force material from the top of the container downwardly. Thus, the material is thoroughly mixed and kneaded. At the conclusion of the mixing operation, the vacuum is removed from lines 31} and 31 and the bowl is lowered to a position in which it can be removed from the mixer.

During operation of the mixer, the various gears and bearings are lubricated by a system which includes a gear driven pump (not shown) mounted upon transverse plate 57. It is to be understood that the space above plate 57 functions as an oil sump so that the pump has an inlet line disposed just above the plate. The pump supplies oil under pressure through tubes 68 to cylindrical housing sections 63, 64 and 65. Oil flows from these sections through transverse bores 72 and vertical bores 71 in the three agitator shafts. The i1 is discharged from the top ends of bores 71 of agitator shafts 16 and 17 onto upper bearings 117. The oil drops from these bearings to= lubri cate gears 115, 116 and sun gear 47. Similarly, oil flows from vertical bore 71 and center shaft 15 outwardly through a transverse bore 151 formed in that shaft just below plate 103. Gil flowing outwardly through this upper transverse bore drops over bearing 43 and flows outwardly through transverse ports 152 and flows over bearing 45. Oil dropping from bearing 45 is caught by annular plate 153 and flows inwardly through ports 154-. The oil then drops downwardly over lower bearings 44.

From the foregoing discussion of the general principles of the present invention and the above description of a preferred embodiment, those skilled in the art will readily comprehend various modifications to which the invention is susceptible. For example, it is obvious that four planetary shafts and agitator blades similar to those shown could be employed if desired. Therefore, I desire to be limited only by the scope of the following claims.

Having described my invention, I claim:

1. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a speed twice that of the center shaft, a center agitator blade mounted upon said center shaft, said agitator blade having four arms extending generally radially outwardly therefrom, each of said arms presenting a concave leading face and a convex trailing face, said planetary shaft having a planetary agitator blade mounted thereon, said planetary agitator blade having two equi-spaced radial arms, each of said last named radial arms having a concave leading surface and a convex trailing surface.

2. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a speed twice that of the center shaft, a center agitator blade mounted upon said center shaft, said agitator blade having four radial arms extending outwardly therefrom, each of said arms presenting a concave leading face and a convex trailing face, said planetary shaft having a planetary agitator blade mounted thereon, said planetary agitator blade having two equi-space radial arms, each of said last named radial arms having a concave leading surface and a convex trailing surface, the trailing faces of the arms of the planetary agitator passing closely adjacent to the leading faces of the arms of the center agitator.

3. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said up posite direction at a speed twice that of the center shaft, a center agitator blade mounted upon said center shaft, said agitator blade having four radial arms extending outwardly therefrom, each of said arms presenting a concave leading face and a convex trailing face, said planetary shaft having a planetary agitator blade mounted thereon, said planetary agitator blade having two equi-spaced radial arms, each of said last named radial arms having a concave leading surface and a convex trailing surface, the trailing faces of the arms of the planetary agitator passing closely adjacent to the leading faces of the arms of the center agitator, the last named trailing face and leading face extending substantially parallel to one another when the arm of the planetary blade and the arm of the center blade reach a position of maximum intermesh.

4. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a speed twice that of the center shaft, a center agitator blade mounted upon said center shaft, said agitator blade having four radial arms extending outwardly therefrom, each of said arms presenting a concave leading face and a convex trailing face, each of said arms being angulated so as to form an individual helix, said planetary shaft having a planetary agitator blade mounted thereon, said planetary agitator blade having two equi-speed radial arms, each of said last named radial arms having a concave leading surface and a convex trailing surface, each of said last named arms being angulated so as to form an individual helix.

5. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotafing said planetary shaft about its own axis in said opposite direction at a speed twice that of the center shaft, a center agitator blade mounted upon said center shaft,

said agitator blade having four radial arms extending outwardly therefrom, each of said arms presenting a concave leading face and a convex trailing face, each of said arms being angulated so as to form an individual helix, said planetary shaft having a planetary agitator blade mounted thereon, said planetary agitator blade having two equispaced radial arms, each of said last named radial arms having a concave leading surface and a convex trailing surface, each of said last named arms being angulated so as to form an individual helix, the helix angle of said arms on the planetary agitator being twice that of the helix angle on the arms of the center agitator.

6. A mix-er comprising a center shaft and a pair of planetary shafts disposed upon opposite sides of said center shaft, each of said planetary shafts extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shafts planet-wise around said center shaft in the opposite direction, and means for rotating each of said planetary shafts about its own axis in said opposite direction at a speed twice that of the center shaft, a center agitator blade mounted upon said center shaft, said agitator blade having four radial arms extending outwardly therefrom, each of said arms presenting a concave leading face and a convex trailin face, each of said planetmy shafts having a planetary agitator blade mounted thereon, each of said planetary agitator blades having two equi-spaced radial arms, each of said last named radial arms having a concave leading surface and a convex trailing surface.

7. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having a concave leading face, a convex trailing face and an outer tip, a planetary agitator mounted upon said planetary shaft, said planetary agitator having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of the planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance.

8. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having a concave leading face, a convex trailing face and an outer tip, a planetary agitator mounted upon said planetary shaft, said planetary agitator having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of the planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance, and the trailing surface of said planetary agitator being configurated so that a tip of the center agitator sweeps over said trailing surface at a substantially uniform distance.

9. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having a concave leading face, a convex trailing face and an outer tip, each of said arms being angulated so as to form an individual helix, a planetary agitator mounted upon said planetary shaft, said planetary agitator having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of the planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance, ,-each of said last named arms being angulated so as to form an individual helix.

10. A mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first d rection, means for moving said planetary shaft planet-wise around said cencenter agitator comprising four equi-spaced radial arms, 7

each of said arms having a concave leading face, a convex trailing face and an outer tip, each of said arms being angulated so as to form an individual helix, a planetary agitator mounted upon said planetary shaft, said planetary agitator having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of the planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance, and the trailing surface of said planetary agitator being configurated so that a tip of the center agitator sweeps over said trailing surface at a substantially uniform distance, each of the arms on said planetary agitator being angulated so as to form an individual helix.

11. A vertical mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having a concave leading face, a convex trailing face and an outer tip, each of said arms being angulated so as to forman'individual helix, the helix angle extending upwardly in the direction of advancement of said arms, a planetary agitator mounted upon said planetary shaft, said planetary agitator having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, aconvex trailing surface and an outer tip, the configuration of the leading surface of said center agitator 'being such that a tip of the planetary-agitator sweeps over the leading surface of said center agitator at a substantially uniform distance, each of said'last named arms being angulated so as to form an individual helix, the helix angle extending upwardly in the direction of advancement of said arms.

12. A vertical mixer comprising a center shaft and a planetary shaft extending parallel to said center shaft, means for rotating said center shaft in a first direction, means'for moving said planetary shaft planet-wise around said center shaft in the opposite direction, and means for rotating said planetary shaft about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having aconcave leading face, a convex trailing face and an outer tip, each of said arms being angulated so as to form an individual helix, the helix angle extending upwardly in the direction of advancement of said arms, a planetary agitator mounted upon said planetary shaft, said planetary agitator having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of the planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance, each of said last named arms being angulated so as to form an individual helix, the helix angle extending upwardly in the direction of advancement of said arms, the helix angle of the planetary agitator arms being substantially twice the helix angle of the center agitator arms.

13. A vertical mixer comprising a center shaft and two planetary shafts disposed on opposite sides of said center shaft and extending parallel to said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shafts planet-wise around said center shaft in the opposite direction, and means for rotating each of said planetary shafts about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having a concave leading face, a convex trailing face and an outer tip, a planetary agitator mounted upon each of said planetary shafts, each of said planetary agitators having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface, a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of a planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance.

14. A vertical mixer comprising a center shaft and tWo planetary shafts extending parallel to said center shaft and disposed on opposite sides of said center shaft, means for rotating said center shaft in a first direction, means for moving said planetary shafts planet-wise around said center shaft in the opposite direction, and'means for rotating each of said planetary shafts about its own axis in said opposite direction at a rate of speed twice that of the center shaft, a center agitator mounted upon said center shaft, said center agitator comprising four equi-spaced radial arms, each of said arms having a concave leading face, a convex trailing face and an outer tip, a planetary agitator mounted upon each of said planetary shafts, each of said planetary agitators having two equi-spaced radial arms formed thereon, each of said arms having a concave leading surface a convex trailing surface and an outer tip, the configuration of the leading surface of said center agitator being such that a tip of a planetary agitator sweeps over the leading surface of said center agitator at a substantially uniform distance, and the trailing surface of each of said planetary agitators being configurated so that a tip of the center agitator sweeps over said trailing surface at a substantially uniform distance.

References Cited in the file of this patent UNITED STATES PATENTS 1,762,081 Schleicher June 3, 1930 2,457,533 Dehufi Dec. 28, 1948 3,046,812 Beaman et a1. July 31, 1962 3,075,746 Yablonski et al Jan. 29, 1963 

1. A MIXER COMPRISING A CENTER SHAFT AND A PLANETARY SHAFT EXTENDING PARALLEL TO SAID CENTER SHAFT, MEEANS FOR ROTATING SAID CENTER SHAFT IN A FIRST DIRECTION, MEANS FOR MOVING SAID PLANETARY SHAFT PLANET-WISE AROUND SAID CENTER SHAFT IN THE OPPOSITE DIRECTION, AND MEANS FOR ROTATING SAID PLANETARY SHAFT ABOUT ITS OWN AXIS IN SAID OPPOSITE DIRECTION AT A SPEED TWICE THAT OF THE CENTER SHAFT, A CENTER AGITATOR BLADE MOUNTED UPON SAID CENTER SHAFT, SAID AGITATOR BLADE HAVING FOUR ARMS EXTENDING GENERALLY RADIALLY OUTWARDLY THEREFROM, EACH OF SAID ARMS PRESENTING A CONCAVE LEADING FACE AND A CONVEX TRAILING FACE, SAID PLANETARY SHAFT HAVING A PLANETARY AGITATOR BLADE MOUNTED THEREON, SAID PLANETARY AGITATOR BLADE HAVING TWO EQUI-SPACED RADIAL ARMS, EACH OF SAID LAST NAMED RADIAL ARMS HAVING A CONCAVE LEADING SURFACE AND A CONVEX TRAILING SURFACE. 